Then, the patient underwent tumor resection. Surgery revealed a mass (95x100 mm), with soft texture, which was located at the retrorectal-presacral space. The surgical specimen was reported as ARMS after pathological evaluation. Microscopically, neoplastic cells had large, pleomorphic nuclei with considerable pleomorphism. Bizarre multinucleated giant cells with abundant eosinophilic cytoplasms were also present (Fig. 3A). Immunohistochemical evaluations revealed positive staining for CD99, vimentin, CD34, and Desmin (Fig. 3B). The staging of this patient was stage-I according to the American Intergroup Rhabdomyosarcoma Study (IRS). After surgery, the patient was treated with combination chemotherapy. Vinorelbine, ifosfamide, and actinomycin D were administered intravenously. At 23 months follow up, the patient was asymptomatic with no evidence of metastases or local recurrence. He underwent a metastatic work-up that included a thoracic and abdominal CT scan with and without contrast enhancement and a total body bone scan. These results were negative for tumor.
RMS is the most common sarcoma in the pediatric population, and it is very uncommon in adults, it is thought to arise from immature mesenchymal cells that are committed to skeletal muscle lineage, but these tumors are also known to arise in tissues in which striated muscle is not normally found. RMS is classified into 4 major subtypes, embryonal RMS (ERMS), alveolar RMS (ARMS), pleomorphic RMS (PRMS) and spindle cell/sclerosing RMS (SRMS). ARMS is most commonly seen in older children and young adults.
RMS can occur at various sites in the body, such as the head, neck, trunk, and extremities, including sites lacking normal striated muscle cells. The most common primary site in adults is the extremities, and the head and neck parameningeal region is the most common site in children. Available data on the extremely infrequent localisations of adulthood, such as larynx, renal pelvis, subcutaneous tissue, uterine, retroperitoneal space, and so on, are insufficient and scarce, mostly presented as case reports or single institution experiences with small numbers of patients. In fact, our patient is the first single-case report of ARMS arising from the retrorectal-presacral space in an adult male, within our thorough investigation.
There are multimodality treatment options for adult RMS, including surgery, radiation therapy for control of residual bulk or microscopic tumor and systemic combination chemotherapy for primary cytoreduction and eradication of gross and micrometastases. Complete surgical resection is the mainstay of curative therapy to ablate the disease for early tumor stage in the absence of distant metastases. All patients with RMS must receive combination chemotherapy as soon as diagnosis is made or after resection. It improves survival significantly. RMS generally has a dismal prognosis, which has been described in most reports. The best prognostic factors are stage I with small size, less than 5 cm, absence of nodal involvement, and young age, less than 10 years. The 51-year-old male patient in our case underwent tumor resection and received combination chemotherapy and achieved a satisfactory outcome, and so far he is being followed up.
In conclusion, this case has reminded us that ARMS could occur in uncommon site and older male. All radiologists should be aware its imaging features. Improvements in imaging in addition to early surgical intervention and chemotherapy treatment are crucial to improve survival chances. An accumulation of such cases is needed for further evaluation and research.
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